Extralite offer a 142x12mm rear hub but no Sram XX1 freehub option.
MarcoL said:
I prefer a lightweight carbon rim than a lightweight aluminum rim at the same weight,
It is not very easy to decide which one is best, since if you broke the wheel you will broke some bones
Which one do you think is best? The one on /r2 or the extralite?
Although it's not listed on their website wheelset page when you go to the website hub page Extralite do have a Sram XX1 freehub now.
Extralite HyperRear
Extralite are one of those companies that I always have mixed feelings about. Their parts are some of the lightest around but that weight saving comes at the price of longevity. Things like the threads that allen bolts screw into are pared down so you only have a few turns available. The threads in my (2009 vintage) Extralite stem were looking close to stripping, which is another reason why I replaced it. The Extralite brass coloured parts are light but that metal is very soft. Where it's used for any sort of threads or allen bolts you have to be careful.
I bought an Extralite Ultrastar2 headset expander and that was terrible. It didn't clamp tightly enough in the RockShox steerer to be able to adjust the headset bearings, and then to finish it off the 8mm allen bolt rounded. I had to hammer it out of the steerer tube. At the same time I bought an Extralite cassette lockring. It didn't have enough thread length to even start tightening on a Sram cassette. Total waste of €48 euros that was.
Saying that, my Extralite front hub was fine without any issues. The Extralite HyperRear hub has a cautionary note on its product page about the freehub mechanism:
"It took more than a year of continuous testing to develop and fine tune the HyperRear full-alloy front-engagement freewheel mechanism.
This new device is able to manage extremely high torque values, it offers 36 quick engagement positions for a precise feel and a minimal friction resistance.
Oversized front engagement freewheel offers a much wider teeth engagement surface to spread the transmission torque on, handles over half-ton of chain pull.
It is a racing assembly sensibly stronger and lighter than our conventional pawls systems, as counterpart coasting is more noisy.
Mileage of freewheel parts is also lower than conventional pawls systems however wearable parts can be easily replaced." Extralite
I'd be inclined to buy some spare freehub bodies at the same time as the Extralite wheels if you go that route. I only bought a front Extralite hub as I was using my Powertap hub for the rear wheel.
When it comes to the rims themselves I don't know. With newish products you could either wait for more rider feedback to see how solid they are or buy the rims from somewhere that you know is reputable. A store who will definitely look after you if there are any warranty problems.
Back on planet earth, I'm keen to try out the Crossmax 29 SLR. At 1620 with an alloy rim, that looks to be a good bet for an all-round wheel. I've got Mavic wheels on family bikes, but would happily own another set.
Unless you're sponsored by Mavic or refuse to use carbon rims (both valid reasons) they don't seem to offer much. Their main selling point hopefully being rim durability I guess. The 2013 Mavic Crossmax 29 SLR wheels are £784.99 GBP ($1268 USD / €959 euros).
Chain Reaction Cycles - 2013 Mavic Crossmax 29 SLR Wheelset
That's not cheap for what's a relatively heavy 1620g wheelset with proprietary spokes and a 19mm inside rim width. Crossmax SLR wheels were highend in 2008 but they haven't kept pace with technological change since then. The increased availability of stiff, wide, affordable and (mostly) reliable carbon fibre rims in 2013 makes them a much harder sell. You could have a set of Roval Control carbon 29 wheels 1580g and a 22mm inside rim width for about the same price.
Specialized Bicycle Components
2013 Specialized Wheels & Tires - Aero & Disc Road, Budget Carbon 29er MTB & More! - Bike Rumor
An example of what they're competing against for all round everyday training wheels if you're on a budget would be these light-bicycle.com all mountain wheels 1500g, 23mm inside rim width for £400 GBP ($646 USD / €488 euros) including shipping, which are available in a reinforced rim version. Used with a wide tyre a wider inside rim width gives a better tyre profile for improved grip and handling.
all mountain 29er carbon mtb wheels clincher tubeless wheel ready - light-bicycle
For race wheels the 1620g Crossmax SLR wheelset would be giving away 170g in weight to the stock 1450g Roval Control SL 29 wheelset on your S-Works Epic, and 460g to something like the 1160g Extralite CarboCamber wheels.